'Exotic Galaxy' With Black Hole Heart Wows Astronomers

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A strange, newfound galaxy may help astronomers figure out how
black holes and star formation evolved in the early universe,
according to a new study.

The
spiral galaxy, dubbed Speca, boasts fast-moving jets of
particles rushing from its center, a phenomenon more commonly
observed in elliptical galaxies. In fact, Speca is just the
second spiral known to have such jets.

These jets are spawned by a supermassive
black hole at the heart of Speca. Researchers hope studying
the galaxy will yield insights into black holes, star birth and
the interaction between the two.

"This is probably the most exotic galaxy with a black hole ever
seen," said the study's principal investigator Ananda Hota, of
the Academia Sinica Institute of Astronomy and Astrophysics
(ASIAA), in Taiwan, in a statement. "It has the potential to
teach us new lessons about how galaxies and clusters of galaxies
formed and developed into what we see today." [ Photo
of the spiral galaxy Speca ]

A strange radio galaxy

Speca — whose name is short for Spiral-host Episodic radio galaxy
tracing Cluster Accretion — is found about 1.7 billion
light-years from Earth. In addition to being a spiral, it's
what's known as a radio galaxy.

At the heart of a radio galaxy lies a supermassive black hole.
Material surrounding it is thrust outward at relativistic speed,
forming jets that shine brightly at radio frequencies. [ Images: Black
Holes of the Universe ]

These relativistic
jets aren't constant; they ebb and flow with time, likely
dependent on the material that fuels them. Over time, the
material diffuses into lobes, much as water flowing from a hose
spreads out as it slows down.

Most radio galaxies discovered to date are elliptical. Elliptical
galaxies tend to be old, without a lot of new star formation,
while spirals host much more star birth. So it's intriguing,
researchers said, to find a jet-spewing spiral; studying Speca
could help them better understand how spirals morph into
ellipticals over time.

"How black holes stop star formation is still not observed," Hota
said. "Speca is an opportunity to investigate these details."

Speca's structure

Astronomers used a variety of telescopes to characterize Speca,
finding that it boasts three pairs of lobes. Such a high count is
rare even among ellipticals, and it provides clues about the
evolution of Speca.

According to Hota, the smallest, closest pair is most likely only
a few million years old. The middle lobes fall between 10 and 100
million years old.

But it is the outermost pair that yields the biggest surprise.
With an age of several hundred millionyears, the cloud of
material spewing from the center of the galaxy diffused long ago,
becoming less active over the years.

At some point, however, the material collided with energetic
particles streaming throughthe
galaxy cluster surrounding Speca. These collisions revived
the ancient remnants, providing astronomers with a greater
understanding of the environment within the cluster.

The research was published in the August issue of the Monthly
Notices of the Royal Astronomical Society.

Understanding star formation

Spiral galaxies eventually transform into ellipticals, and Hota
thinks the presence of jets may affect this shift.

"What I believe is that this trend of radio galaxies found always
in ellipticals and not in spirals is an end-product of multiple
galaxy mergers and multiple episodes of jet feedbacks, happening
over a few billion years time," Hota said.

The two combined phenomonena would slowly consume the materials
needed for star formation, allowing a spiral galaxy to morph
into an elliptical. This meshes well with current theories about
how ellipticals form; the ejection of material simply speeds the
process along.

"These jets are supposed to remove a large fraction of gas from a
galaxy and stop further star formation," Hota said. "If the
galaxy is gas-rich in the central region, and as the jet
direction changes with time, it can have an adverse effect on the
star formation history of a galaxy."

Speca provides astronomers with an opportunity to study the
effect of the jets on a young galaxy. Since they stem from the
supermassive black hole at the galaxy's center, it reveals a
connection between the powerful behemoth and the birth of new
stars.

"Once we understand how star formation and black hole activity
evolved with time, we will have clues on the co-evolution
processes," Hota said.